Semiconducting polymer dots (Pdots) represent a new class of highly fluorescent nanoparticles with emissions tunable from the visible to the near IR region. The fluorescence intensity, e.g., of a single green-emitting Pdot can be about 30 times brighter than a single quantum dot of similar emission wavelength (Qdot565) when excited with a 488-nm laser. In addition, most Pdots exhibit excellent photostability without blinking. Previous studies have also shown that Pdots have good biocompatibility. These fluorescence properties and good biocompatibility of Pdots make them excellent probes for cellular imaging and bioassays.
Functionalizing the surface of Pdots and controlling their colloidal stability are an important consideration in translating Pdots for use in biological studies. For example, a highly charged particle can be important in many cases for colloidal stability, especially under conditions of high ionic strength, which is often encountered in biological applications. Unfortunately, many particles can aggregate over short periods of time in high ionic strength solutions due, e.g., to surface properties of the particles.
Thus, there is a need for polymer dots and compositions having improved colloidal stability in solutions, e.g., having a high ionic strength. Methods of making the polymer dots having improved colloidal stability are also desired.